I have a job configured with "branches to build" as "origin/release/flow". The polling log shows that the git plugin is erroneously only using the last component of the branch name to poll:
git ls-remote -h firstname.lastname@example.org:org/Repo.git flow # timeout=10
This matches six branches on the server. The plugin uses the first one, which is "refs/heads/appstore/flow". The hashes never match, so the plugin triggers the build every time.
As a workaround I've changed "branches to build" to "refs/heads/release/flow", but this should be fixed.